1. Field of the Invention
The present invention relates to a surgical system for cutting tissue.
2. Description of Related Art
There are many surgical procedures that require the cutting and aspiration of tissue. For example, in a retina re-attachment procedure the surrounding vitreo tissue must be removed before the retina is repaired. The cutting device must be delicate enough to remove the tissue without further damaging the retina. Prior art ophthalmic cutting devices include an inner sleeve that moves relative to an outer port of an outer sleeve. The sleeves are coupled to a vacuum system which pulls tissue into the outer port when the inner sleeve moves away from the port. The inner sleeve then moves in a reverse direction past the outer port to sever the tissue in a guillotine fashion. The vacuum system draws the severed tissue away from the outer port so that the process can be repeated.
The inner sleeve is driven by a motor located within a hand piece that is held by the surgeon. The inner sleeve is typically coupled to the motor by a rotating lever mechanism. Rotating lever mechanisms of the prior art are relatively large and complex. Additionally, the stroke and duty cycle of the inner sleeve is fixed for each device. It would be desirable to provide a surgical guillotine cutter that is inexpensive to produce, small in size and would allow a surgeon to vary the stroke and duty cycle of the inner cutter.
Guillotine cutters are typically provided with a control system that allows the surgeon to vary the vacuum pressure of the aspiration line. U.S. Pat. Nos. 4,395,258; 4,493,698; 4,706,687 and 4,838,281 issued to Wang et al. and Rogers et al., respectively, disclose systems for controlling the vacuum pressure of a guillotine cutter. The Wang/Rogers systems include a solenoid actuated valve that is coupled to the hand piece and controls the flow of fluid in the aspiration system. The position of the valve and the corresponding vacuum of the system is controlled by an input signal provided to the solenoid by a control circuit. The input signal is typically the summation of a feedback signal and a control signal that is generated by a potentiometer. The feedback signal corresponds to the actual vacuum pressure measured in the system. The potentiometer is typically a foot pedal that is manipulated by the surgeon.
The surgeon controls the vacuum pressure by depressing the foot pedal and varying the amount of air flow through the solenoid control valve. Because of the inertia within the system, there is typically a lag between the input command of the surgeon and the actual variation of vacuum pressure at the tip of the cutter. It would be desirable to provide a vacuum control system that has a more rapid response time than systems of the prior art.
Additionally, prior art guillotine cutters typically do not have many control functions, or safety features to prevent inadvertent damage to the eye. For example, prior art systems do not automatically compensate for variations in the load on the cutter. The surgeon must observe a reduction in cutting rate and then manipulate the cutter and the vacuum pressure to overcome the increased load. Additionally, with a prior art cutter, if the cutter ceases to operate while the vacuum pressure is applied to the system, the tissue may be pulled into the aspiration port of the outer sleeve. Such an event may damage the eye. It would be desirable to provide a guillotine cutter which has a number of control functions and safety features.
Cutting tissue sometimes causes undesirable bleeding which must be coagulated. Coagulation can be performed with an electro-cautery device. To coagulate the tissue the cutter is removed and an electro-cautery device is inserted into the patient. To continue cutting, the electro-cautery device must be removed to allow re-insertion of the cutter. Such a procedure is time consuming and may reduce the safety of the procedure. It would be desirable to provide a cutter that can also cauterize tissue.